RaiderZ is a Free-to-Play Massively Multiplayer Online RPG (or MMORPG for short) in which players engage in battle against colossal and powerful beasts in order to save the world of Rendel from destruction.
Most popular community and official game content for the past week.  (?)
What does popular mean?
It means the content you're seeing has been rated up more than it has been rated down for the given time period.